Apparatus for drying strip material



Dec. 2, 1958 J. DUNGLER 2,862,305

APPARATUS FOR DRYING STRIP MATERIAL Filed July 6. 1954 2 Sheets-Sheet lI F/y. 6

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Dec. 2, 1958 J. DUNGLER 2,862,305

APPARATUS FOR DRYING STRIP MATERIAL Filed July 6, 1954 2 Sheets-Sheet 2OOOOOO m OOPOO United States Patent O 2,862,305 I APPARATUS FOR DRYINGSTRIP MATERIAL .lulien Dungler, Basel, Switzerland Application July 6,1954, Serial No. 441,337 Claims priority, application France July 29,1953 2 Claims. (Cl. 34-68) The present invention relates to means fordrying strip or web material, such as fabrics, papers, pulp, sugar andother permeable or liquid containing materials by means of a treatmentfluid, in particular a gaseous fluid.

It is one of the objects of the present invention to provide meansaffording marked improvements in drying of materials of the aforesaidcharacter, including extreme rapidity of drying performance, economy andreduction in the overall dimensions of the equipment thereby used, asthe treatment fluid may now be used at increased temperatures materiallyfar above any temperatures heretofore or usually applied. a

It was up till now possible to expose during drying a productimpregnated with a liquid to a temperature higher than the temperaturewhich such product ordinarily would withstand in a dry condition. Suchan increased or higher temperature ranges between 100 C. and 200 C.Furthermore, it is common practice to dry a product by directing uponthe latter infra-red radiations or other rays emitted by specialradiation sources to reach required temperatures.

Drying according to this invention is carried out by a treatment fluidwhich is circulated, and of which at least some components are broughtup to a temperature so that the fluid itself and any metal or likeelements located in the treatment chamber, such as fluid guiding means,which direct the treatment fluid for contact with the product to bedried, emit radiations which eflicaciously contribute to considerablyincreased drying effect of the product under treatment, in addition tousual convection heat.

According to another feature of this invention, the treating fluid isheated to a temperature above at least 200 to 250 C.

It is still another object of this invention to provide means affordingheating of the treatment fluid to its required temperature by thecombustion of a fuel carried out in a treatment chamber or in a separateenclosure which is in communication with said chamber, so thatthe'treatment fluid resulting therefrom consists partly at least ofburnt fuel gases produced in this combustion.

It is a further object of this invention to provide means performing thecombustion for heating the treatment fluid under admission of air, insuch manner which ensures complete combustion without leaving any excessof air in the treatment chamber.

It is still another object of this invention to provide means ensuringpromotion of irradiations from the circulating treament fluid, which isheated to a temperature sufliciently high enough to inherently produceheat by convection and radiation, particular radiant elements beingpreferably disposed along the path of the treatment fluid, which impartto the product under treatment radiation eflect without disturbing thecirculation of the fluid.

Yet another feature of this invention is to provide 2,862,305 PatentedDec. 2, 1958 ICC means imparting a relatively high radiation emittingpower to the surface of at least some of the radiant elements which aredevoid of any special heating source and are located in the treatmentchamber, such as guiding or nozzle elements for said treatment fluid.

Still another feature of this invention resides in drying the materialby the simultaneous application thereto of heat by convection andradiant heat.

According to this invention, the introducion of the product to betreated into the treatment chamber is effected by means of asubstantially inert strip of a material, which is usually not affectedby the condition or conditions prevailing in the treatment chamber, suchas asbestos or the like, whereby such asbestos strip is advanced aheadof the product under treatment, said strip having a length so that thedrying or like treatment machine may be initiated and its output rateproperly adjusted, prior to the admission of the product proper into thetreatment chamber.

Still another object of this invention is to provide means conducive toa highly economical treatment plant of the type hereinabove stated, inwhich excess fluid built up inone treatment chamber, i. e., essentiallyby virtue of the evaporation of the liquid with which the treatedproduct is impregnated, is used for the further supply of treatmentfluid in another treatment chamber without the necessity of any specialheat exchanger.

It is still a further object of the invention to provide means renderingthe possibility of discharging the treated product from the treatmentchamber substantially before the dryness degree requisite for therespective product is obtained, the drying operation being automaticallycompleted outside the treatment machine or plant, owing to the heatstored within the treated product at the moment when the latter leavesthe treatment chamber.

It is still another object of the invention to provide meansfacilitating the disposition of the nozzle means so as to form avertical, inclined or horizontal treatment path, whereby in the case ofa vertical passageway or path obtained by the nozzles, the material(pulp, for example) to be treated may be introduced into the dryer bygravitation, rather than by pulling forces.

Other objects and advantages of this invention will appear from thefollowing specification and claims, reference being had to theaccompanying drawings in which:

Fig. 1 is a sectional view of a machine according to the presentinvention,

Fig. 2 is a cross section of the machine of Fig. 1,

Fig. 3 is a section taken on line IIIIII of Fig. 2,

Fig. 4 is a section of detail employed in the invention and drawn to anenlarged scale,

Fig. 5 is a diagram aiding in the explanation of the invention,

Fig. 6 is a fragmentary and enlarged vertical sectional view through anupper screen with blowing nozzles employable in the invention,

Fig. 7 is a horizontal sectional view taken along lines 7-7 of Fig. 6,

Figs. 8 and 9 are similar horizontal sectional views as seen in Fig. 7,but showing screens with modified shapes of perforations.

Referring now more particularly to Fig. 2, there is disclosed atreatment chamber forming a highly heat-- insulated enclosure with alower portion 1 and a removable upper portion 2.

Within this treatment chamber are accommodated a 382,221, filed October9, 1953.

To the lower blowing nozzles 4 are coordinated upper blowing nozzles 5suspended from a bracket 6, in the upper portion of the treatmentchamber. The fluid discharge slots 7 and 8 of the nozzles 4 and 5,respectively, form a boundary for the path of travel of theprodnct 9 tobe treated in the treatment chamber 1. It should he pointed out thatthis product is not supported by any supporting member whatever duringits traversal of the treatment chamber, it is rather maintained alongits path by the action of the discharged drying fluid, and possibly bythe longitudinal traction or pulling force exerted on the product byexternal drawing means. In fact, any supporting member whatever duringits traversal of the reach too high a temperature liable to cause thetreated product to be damaged when getting into direct engagement withsuch heated supporting means.

The supply of treatment fluid to the nozzles 4 and 5 is performedthrough lateral collectors 10 and 11, supplied by a blower 12 arrangedin the lower portion of the treatment chamber under a metal sheetpartition 13 extending about half the cross section of the treatmentchamber, the other half of the chamber being separated from theenclosure which covers the blower 12 by a wire screen 14.

Due to the high temperature conditions of operation, means for drivingthe blower 12 should be arranged outside the treatment chamber and theshaft 15 of the blower is to be efficiently cooled. The shaft 15 whichis supported in two bearings 16, 17 (Fig. 4) placed outside thetreatment chamber carries at one of its ends a pulley 18 for a V-shapedbelt transmission and adjacent the bearings 16 and 17, discs 19 havingventilation ribs 20 for air-cooling the bearings.

The shaft 15 is hollow and contains in its bore 22 a stationary andperforated pipe 21 which may be provided inside its bore with holes 23.This pipe 21 passes through a stationary drum 24, into which extends theopen end of the shaft 15 and which is fitted at its lower part with adrain conduit 25. The pipe 21 is supplied with a cooling fluid, such as,compressed air or water, which gathers within the drum 24 and flows outthrough the conduit 25 after having cooled the shaft 15 whilecirculating in the bore 22.

Heating of the treatment fluid may be effected, according to a featureof this invention, by the combustion of gas, fuel, the fuel and the airbeing directly and simultaneously supplied to the treatment chamber. Tothis end, a gas or fuel-oil pipe 26 enters through an opening 27 thetreatment chamber 1 below the wire screen 14. Said pipe is fitted withburners 28 supplied with fuel and air in such proportion as to secure acomplete combustion without any excess of air.

According to another feature of this invention, wire screens 29, 30 madefrom perforated sheet metal 33 and pervious to the treatment fluid, theend and function thereof will be explained hereinafter, are arrangedalong the travel path of the treatment fluid in a directionsubstantially parallel to the treated product 9 and spaced therefrom arelatively short distance.

The fluid in excess is discharged from the treatment chamber throughflues or stacks 31 the cross section of which is controlled by valves orflap means 32 manually or automatically operated in any desired manner.

By operating the machine which has just been described, the inventionmay be put into practice as follows:

When the operation is initiated, the drying chamber is filled with air.After the burners 23 have been lit up, the blower 12 is started and thetemperature progressively increases in the treatment chamber. As soon asthe desired temperature is reached, the air contained in the chamber maybe, if desired, expelled by means of a direct steam jet introducedthrough discharge means (not shown). Such an operation is however notnecessary since the steam produced by the evaporation of the liquid withwhich the treated product is impregnated is soon substituted for theair. It should be noted that this operation takes place in a very shorttime owing to the small capacity of the treatment chamber (note thesmall number of blowing nozzles as compared with that in I similartreating machines of known construction) and the short time required forthe drying operation.

Since the machine is to be operated at a very high temperature, namely,above 250 C., the treated product, for instance, fabric, should not beintroduced into the treatment chamber until accurately determinedoperating conditions are secured, so as to prevent any damage to thefabric. To this end, a strip of an incombustible material, such asasbestos or the like, is attached to one end portion of the fabric.

This strip is then introduced into the machine and the length of thisstrip of asbestos is predetermined in a manner, such as to afford enoughtime for the necessary adjustments, particularly the adjustment of thetemperature and/or the rate of feed, to be carried out before the fabricproper enters the treatment chamber. Preferably, the operation isinitiated with a rate of feed above that necessary for normal operation,such rate of feed being then progressively reduced until the desireddegree of dryness is reached.

According to an essential feature of this invention, the circulatingtreating fluid is heated above a temperature, for instance, 250 C., sothat the drying effect is not only obtained by direct transmission ofheat through contact between the treating fluid and the material, butalso by irradiation effect of at least some components of the fluid andby additional heat radiating elements which are located in the treatmentchamber and consist mainly of elements for guiding the treating fluid,whereby through emission of radiations the drying effect is favorablyincreased and becomes highly economical. In fact, if the treatment fluidhas a temperature of about 250 C., any elements which come into contactwith the circulating fluid, particularly the walls of the nozzles 4 and5 as 'well as the surfaces of the wire screens or perforated means 29and 30 provided for this purpose (having variously shaped perforations34, 35, 36, 37 according to Figs. 6 to 9), are heated to the sametemperature which promotes the emission of radiations, thus effectivelycontributing to rapid drying of the material by supplying also heat inthe form of radiations. It should be noted that in contradistinction toknown machines provided with special radiation emitting elements heatedto the required temperature by a special heat source, radiationsaccording to the invention are automatically obtained and withoutinvolving any additional consumption of energy or power.

It will be noted that with the process of the invention the lengthy,liquid-impregnated material is moved continuously through the enclosuremeans, while the treating fluid is heated within the enclosure means bya single source of heat to a temperature sufficiently high todeleteriously affect the material when in dry condition.

Separate streams of the heated fluid are oriented for impingement ofthese streams against spaced apart areas on opposite surfaces of thematerial moving through the enclosure means.

Simultaneously with the impingement of the streams of heated fluid onthe material, radiant heat is directed uninterruptedly onto the entiresurface areas of the material, this radiant heat emanating from theheated fluid via radiant heating means and in close proximity to theopposed surfaces of the material, so that the material is dried in theenclosure means by heat convection and radiation. In this way areas ofthe liquid-impregnated material which are treated by the fluid streamsare also exposed to radiant heat.

Furthermore, it should be noted that the circulating fluid isconstituted in the example contemplated, apart from the steam producedby the evaporation of the liquid with which the material or fabric isimpregnated, by combustion gases emanating from the burners 28. Thetreatment fluid thus contains H and CO namely gases with a highabsorption and emitting power. Such gases thus absorb radiations comingfrom the aforesaid walls, which radiations are otherwise unable todirectly reach the material or fabric and will now become useful in thetreatment process.

To increase the radiating eflect, the surfaces of the elements which arelocated in the treatment chamber may be shaped, coated and otherwiseprepared to promote radiation, for instance, by surface strata ofblack-lead or graphite.

-It should further be noted that heating of the treatment fluid may alsobe carried out in a diiferent manner, e. g. by means of electricresistors or through indirect heating means by burning a liquid orgaseous fuel within a tubular element placed inside the suction channelof the blower 12 and wherein the treatment fluid is separated from thecombustion gases which are discharged to the atmosphere. 'In this case,the treatment and radiant fluid is constituted essentially by H O.

Fig. 5 demonstrates for a particular machine of the kind abovedescribed, the increase of efliciency obtained by using the methodaccording to the invention. The diagram of Fig. 5 shows plotted againstthe temperature of the circulating treatment fluid, the quantity ofwater evaporated in kg./m. per hour. While curve I indicates theevaporation due only to the amount of heat transferred by convection tothe treated product, i. e. by direct contact between the treatment fluidand the treated product, curve '11 shows the complete result obtained bythe heat delivered by convection, as well as radiation to the productunder treatment, whereby the difference between curve II and curve Idemonstrates the gain obtained by the process according to theinvention.

It appears from this diagram that the gain obtained by radiation heatreaches a substantial value at temperatures above 200 C. Thus this gainis about 8% at a temperature of 300 C. and 26% at a temperature of 500C. Obviously, such efliciency becomes greater with the increase of thetemperature and it should be noted that it is within the scope of thisinvention to also use temperatures of the order say, of 800 C. up to1500 C. and more. The use of such temperatures is made possible becauseas long as any liquid or impregnant remains in the product the boilingtemperature of the impregnant cannot be surpassed and because of thevery short time the liquid-impregnated product under treatment issubjected to such very high temperature (only seconds according to thequantity of the liquid impregnant contained in the product beforetreatment). There are further no elements present in the treatmentchamber, such as supporting rollers and the like, which heated up tosuch high temperature would engage said product. In this respect, itshould also be noted that it is also the purpose of the invention thatthe time during which the gaseous blowing fluid and the product undertreatment are in contact with each other, be reduced as much as possible(less than one minute).

The fluid in excess originated in the treatment chamber by the activeevaporation is discharged through the stacks 31. It should be observedthat the fluid is discharged at a still high temperature, a conditionwhich makes it possible, according to a feature of this invention, touse it for supplying another treatment chamber or machine of any typeoperated at lower temperature.-

The treated fabric may not necessarily leave the treatment chamber withthe final degree of dryness. In fact,

it is possible to subject the fabric only to a preliminary or incompletedrying operation and to effect the final drying performance in a furthermachine, for instance, a

chine by the heat stored within the fabric at the moment.

the fabric leaves the treatment chamber.

The invention has among others the following advan-' tages heretoforenot yet stated:

An extremely intense and quick drying eflect is obtained by the combinedaction of convection and radiation heat at a temperature which would bedeleterious if it would act on the dry product even at a reduced timelimit of the order of one minute. -It should be noted that suchradiations are not emitted by a particular emitting element wastingenergy, but by elements located in the treatment chamber and heated tothe required temperature by the treating fluid itself withoutnecessitating any further source of heat or consumption of energy.

Owing to the intensity and the quickness of the operation, the overalldimensions of the treating machine are extremely reduced as comparedwith those of known treating machines. Since high temperatures are used,the specific weight of the treatment fluid is reduced to such an extentthat the power absorbed for driving the blower or fan which circulatesthe treating fluid is but a small fraction (for instance /5 or less) ofthat necessary in known machines.

The following examples show comparative production obtainable by a dryerarrangement according to the invention and at diiferent temperatures.For this production a dryer or predryer is used having a length of 1metre v and a width of 1 metre.

Let it be assumed that cotton material is to be subjected to treatmentin accordance with the present invention weighing grams/m. andcontaining about 90% water. The temperature of the treatment fluid isapproximately 140 C. An evaporation of 50 kg./h. will take place at atransit speed of the material passing through the dryer at approximately10 m./min.

If the temperature is increased to approximately 300? C., theevaporation will increase to 140 kg./ h. at a transit speed ofapproximately 29 m./min.

If the temperature however is increased to about 800 C., the evaporationwill be eifectuated at a rate of 600 kg./h. while the material passesthrough the enclosure at a transit speed of m./min. In such latter casethe evaporation will be etfectuated at a rate of 460 kg./h. byconvection and at a rate of about kg./h. by radiation.

It will further be noted that the moisture content of the materialleaving a dryer in which a treatment fluid is used at a temperature ofabout 800 C. will be somewhat above 15% of the normal moisture contentwhich is approximately 6 to 8% for cotton and about 17% for W001.

The aforesaid examples may further elucidate the treatment of materialfirst in a predryer of about 2 meter length in which the treatment fluid(superheated steam, carbon dioxide etc.) is heated up to about 800 C.Thereafter the material is passed through an adjacent second dryersection in which part of the treatment fluid of the first or predryermay be employed at a temperature of about 300 C. This second dryer mayhave a length of about 3 metres. Following said second dryer section,the material may be finally passed through a third dryer section ofapproximately 3 metre length, in which the material is exposed to atreatment fluid of a temperature of 140 to C. and derived from treatmentfluid of the first and/ or second dryer sections.

Thus, the transit speed of the product under treatment would be about370 m./min. It is to be noted that air is generally not suitable as afluid as same at extremely high temperatures contemplated by theinvention, does not produce heat effects through convection andradiation, but only through convection.

The velocity of fluid jets emanating from the nozzles or like blowingelements which may be arranged in vertical, horizontal or inclined rows,may range from 2 to 50 m./ sec. or may be considerably higher, forexample, 150 to 200 m./sec.

It can thus be seen that there has been provided according to theinvention means for treating liquidimpregnated material as hereinabovementioned by a fluid in enclosure means to thereby obtain therein atemperature of above 200 C., said material being treated by impingingonto the latter within said enclosure means fluid, which is at leastpartially condensable, having a temperature above 200 C. at which saidfluid inherently emits heat by convection and radiation and which wouldbe deleterious to the material when in dry condition, and passing saidmaterial continuously at a rate of speed and within less than one minutethrough said enclosure means, so that said treated material leaves thelatter still with a predetermined moisture content approximately abovenormal.

Of course, the treatment according to the invention as well as means orapparatus to carry same into effect and hereinabove given are merelyillustrative; the features and the shape, nature, assembly andarrangement of the parts and elements of the dryer may be modified inany suitable manner (Figs. 7 to 9) without departing from the scope ofthe invention.

Thus, the temperature of the treating fluid may be substantiallyincreased above 300 C. Furthermore, heating of the fluid may be carriedout by any suitable means.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. Apparatus for drying strip-like material in a continuous manner,comprising a treatment chamber through which said material is to becontinuously passed, a plurality of nozzle members positioned withinsaid chamber at spaced locations along and on opposite sides of the pathof movement of said material through said chamber, a source of heated,air-free gaseous medium disposed in said chamber, means for feeding someof said medium to said nozzle members for discharge therethrough againstthe opposite surfaces of said material as said chamber about saidmaterial, whereby both said nozzle members and said perforated means areheated to a temperature at which they radiate heat, to thereby ensurethat drying heat is applied to said material both by direct contactthereof by said gaseous medium and by heat radiation emanating from saidnozzle members and said perforated means due to contact thereof withsaid gaseous medium.

2. in apparatus for drying moving strip-like material in a continuousmanner by the simultaneous eflect of heat of a circulating gaseousmedium and radiant heat; a plurality of radiating elements positionedalong the path of movement of said material and oriented substantiallyparallel to said path and transversely to the direction of circulationof said gaseous medium about said material, said radiating elementsbeing pervious to said medium and spaced a short distance away from saidpath and adapted to be brought into heat-radiating condition by saidgaseous medium whereby one and the same gaseous medium serves to applydrying heat directly to said material by contact therewith and toinitiate radiation of heat by said radiating elements for applyingadditional drying heat indirectly to said material.

References Cited in the file of this patent UNITED STATES PATENTS1,125,659 Coe Jan. 19, 1915 1,463,923 Nelson Aug. 7, 1923 2,186,032 MannJan. 9, 1940 2,275,348 Charch et al. Mar. 3, 1942 2,384,990 French Sept.18, 1945 2,389,586 Andrews Nov. 27, 1945 2,391,764 Andrews Dec. 25- 19452,456,301 Miller et al. Dec. 14, 1948 2,590,849 Dungler Apr. 1, 1952

